1. Field of the Invention
The present invention relates to an electromagnetic induction heating snow-melting apparatus for induction-heating rails by electromagnetically induced current supplied from a high frequency power source, thereby eliminating such a situation that rail points are covered by ice and/or snow and thus rendered immovable for switching.
2. Discussion of the Related Art
FIG. 1 is a diagram showing a rail point (switch) included in a railroad track. The rail points are constructed with a pair of basic rails 1 (1R (right) and 1L (left)), a pair of tongue rails 2 (2R and 2L) laying along the basic rails 1, a number of washers 3, and a number of sleepers 4.
The rail points thus constructed, when covered with ice/snow, are frequently inoperable for switching. To cope with this, many types of heating apparatus have been used. Among those heating apparatus, the snow-melting apparatus using electric heaters has predominantly been used. These heaters are used in a state that the heaters are mounted on sleepers or basic rails. Heat generated by the heaters is transmitted to the sleepers or basic rails, thereby melting ice and snow from the rails. In this construction, a relatively large heat quantity, which should be transferred to the rails, is dissipated to the atmosphere. The snow-melting apparatus thus unsatisfactorily functions in the snow-melting performance. Thus, the conventional snow-melting apparatus is not only inefficient but also consumes much electric power.
To solve the disadvantages of the snow-melting apparatus of the heater type, a snow-melting apparatus based on another principle, i.e., electromagnetic induction, that is, a snow-melting apparatus of the electromagnetic induction heating type, has been proposed.
FIG. 2 is a diagram showing the overall construction of the snow-melting apparatus of the electromagnetic induction heating type. FIG. 3 is an enlarged view showing the snow-melting apparatus of FIG. 2. In these figures, reference numeral 1 designates a basic rail; 4, a sleeper; 5, a heating coil; 6, a high frequency power source; and 7, paired lead wires. As shown, heating coils 5 are attached to the outer side walls of the basic rail 1 (heating coils 5 attached to the upper rail 1 in FIG. 2 are indicated by dotted lines because those are disposed on the outside of the rail 1). In operation, the high frequency power source 6 feeds a high frequency current to the heating coils 5 thus attached to the rails 1 by way of the lead wires 7 and cables extending therefrom. At this time, magnetic fluxes B are developed from the heating coil 5 as shown in FIG. 4. Eddy current EC is caused by the magnetic fluxes B to flow in the basic rail 1. PG,4 As a consequent, the rails 1 are heated internally by the eddy currents. Heat loss occurs only in the high frequency power source 6 and in the heating coils 5. Therefore, the heating efficiency is good with less power consumption. This fact is actually confirmed.
In designing the snow-melting apparatus of the electromagnetic induction heating type, design requirements such as heat resistance, weather proof, durability, vibration-proof, and the like are very strict. Further, a high frequency power source must be used exclusively for this apparatus. The cost to manufacture this apparatus is high. For this reason, the snow-melting apparatus of the electromagnetic induction heating type has been not practically used, while the snow-melting apparatus of the electric heater type is widely used because of stability and low equipment cost, it is poor in heating efficiency.
As described above, it is confirmed that the heating efficiency of the electromagnetic induction heating type is good since the rails 1, in effect, generate heat. The heating coil 5, as usually manufactured, is packaged in a molded case. The heating coil packages are then attached to the rails 1 as shown in FIGS. 2 or 3. Accordingly, it must endure the vibrations of rails 1, be mechanically reliable, and must withstand every weather condition. Further, it must have low cost. The heating coils 5 must be simply and easily attached to the rails 1 at the side irrespective of rail length. Where a plural number of coils 5 are attached to the rails 1 of different lengths, it is difficult to standardize the coil attaching work.